Traffic-related air pollution and the brain

Once the healthcare debate in the US moves forward, it is likely that the environment — specifically the reduction of carbon emissions — will become the next priority for President Obama and Congress. Peter and I, as well as many of our colleagues, have worked hard to demonstrate the connections between environmental health and cognitive health by shining the light on neurotoxins in the environment.

So too should we emphasize that the burning of fossil fuels from motor vehicles and from industry may have direct and indirect effects on the brain. It is theorized that particulates from pollution (these being a complex mix of solids and liquids including organic and elemental carbon, nitrates, sulfates, and metals) affect many organ systems in the body.

There is evidence that both short- and long-term exposure to particulates are associated with reduced oxygen supply to the heart (myocardial ischemia), heart attacks, stroke, arrhythmia and sudden death, cardiovascular hospitalization and mortality and blood clotting. Compromised blood flow may contribute to reduced oxygenated blood to the brain over time.

Studies on both humans and animals are beginning to demonstrate links between air pollution and neurodegenerative processes. Comparisons of brain tissues show more pronounced markers of inflammation, oxidative stress, and Alzheimer’s-type pathology in residents of polluted-air cities compared to residents of relatively clean air cities. Children in Mexico City have performed less well on psychometric measures, and MRI scans have revealed higher incidence of abnormal lesions in the prefrontal areas of their brains. Similar lesions have been found in a study of dogs from highly polluted areas, strengthening this worrisome association.

Further, particulate matter has been found in brain tissue and in blood vessels, suggesting that fine particles of pollution may translocate from the lungs and pass through the blood-brain barrier and lodge in the brain where they cause inflammatory processes (elevated cytokines, increase in expression of the COX-2 enzyme, etc) and the deposition of neural proteins such as Abeta42.

Research has also demonstrated that pollution can activate the stress response in our bodies, which I would anecdotally say has been my experience living in a major US city.

I recently caught wind of a compelling study that will be published in next month’s Environmental Research journal, which further strengthens the association between pollution and cognition. The researchers studied nearly 400 women in Germany who had lived at the same address for at least 20 years, and found that those near busy roads were more likely to perform worse on cognition tests. Clearly, a multitude of factors could have influenced the womens’ cognitive performance, but the relationship between proximity to pollution and poorer cognition signals that the link between environmental health and brain health must be taken seriously.

That being the case, I can’t help but wonder whether we should ban all motor vehicles in Congress during healthcare and cap-and-trade negotiations so that common sense will have the best chance of prevailing…?